Heterointerface design and strain tuning in epitaxial BiFeO₃:CoFe₂O₄ nanocomposite films

The ability to control the morphology of heterointerfaces with coupled functionalities is fascinating from both fundamental and technological perspectives. Here, using BiFeO₃:CoFe₂O₄ vertically aligned nanocomposite (VAN) films as a model system, we demonstrate a simple and effective method to modulate the heterointerface and its morphology in nanocomposite films with pulsed laser deposition. By tuning the deposition frequency through thickness during film growth, both vertically straight and gradient heterointerfaces have been achieved. The modulated heterointerface is strongly correlated with strain tuning and interface coupling, and thus modifies the magnetic anisotropy, coercive fields, and ferroelectric switching behavior. This study provides a viable approach for tailoring the interface strain and coupling in VAN and achieving tunable physical properties.